Displacement ventilation: a viable ventilation strategy for makeshift hospitals and public buildings to contain Covid-19 and other airborne diseases

The SARS-CoV-2 virus has so far infected more than 2.4 million people around the world, and its impact is being felt by all. Patients with airborne diseases such as Covid-19 should ideally be treated in negative pressure isolation rooms. However, due to the overwhelming demand for hospital beds, patients are being treated in general wards, hospital corridors, and makeshift hospitals. Adequate building ventilation in hospitals and public spaces is a crucial factor to contain the disease[1][1],[2][2], to exit the current lockdown situation, and reduce the chance of subsequent waves of outbreaks. Lu et al. [3][3] reported an air-conditioner induced Covid-19 outbreak, by an asymptomatic patient, in a restaurant in Guangzhou, China, which exposes our vulnerability to future outbreaks linked to ventilation in public spaces. We demonstrate that displacement ventilation (either mechanical or natural ventilation), where air intakes are at low level and extracts are at high level, is a viable alternative to negative pressure isolation rooms, which are often not available on site in hospital wards and makeshift hospitals. Displacement ventilation produces negative pressure at the occupant level, which draws fresh air from outdoor, and positive pressure near the ceiling, which expels the hot and contaminated air out. We acknowledge that, in both developed and developing countries, many modern large structures lack the openings required for natural ventilation. This lack of openings can be supplemented by installing extract fans. We provide guidelines for such mechanically assisted-naturally ventilated makeshift hospitals, and public spaces such as supermarkets and essential public buildings. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) Grand Challenge grant ‘Managing Air for Green Inner Cities (MAGIC) grant number EP/N010221/1. ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The manuscript contains no data. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3